Large off-road, heavy-duty work vehicles, such as mining vehicles used to haul heavy payloads excavated from open pit mines, are well known and usually employ motorized wheels for propelling or retarding the vehicle in an energy efficient manner. This type of vehicle is shown in FIG. 1. This efficiency is typically accomplished by employing a large horsepower diesel engine in conjunction with an alternator and a main traction inverter. The diesel engine is directly associated with the alternator such that the diesel engine drives the alternator. The alternator is used to power the main traction inverter, wherein the main traction inverter supplies power having a controlled voltage and frequency to two drive motors disposed within the rear wheels of the vehicle. As the drive motor is operated, the drive motor causes a transmission drive shaft to rotate at a low torque and high speed about the drive shaft axis. Because the transmission drive shaft is directly associated with the vehicle transmission, the low torque high speed rotational energy of the transmission drive shaft is communicated to the vehicle transmission. The vehicle transmission then takes the low torque high speed rotational energy supplied by the transmission drive shaft and converts this energy into a high torque low speed rotational energy output which is supplied to the rear wheels.
Referring to FIG. 2, the conversion of this low torque high speed rotational energy into a high torque low speed rotational energy is typically accomplished using a double reduction gear set disposed within the vehicle transmission. A double reduction gear set is a series of gears, pinions and planets that includes a first reduction stage and a second reduction stage. The first reduction stage may include a high-speed sun pinion, a plurality of high-speed planets and a stationary ring gear and the second reduction stage may include a low-speed sun pinion, a plurality of low-speed planets and a stationary ring gear. The output of the first reduction stage is connected to the input of the second reduction stage and may be referred to as the high-speed carrier. In a similar manner, the output of the second reduction stage is connected to the vehicle wheels via a torque tube/hub assembly.
A transmission of the type described above includes a plurality of moving parts that interact and mesh with each other in order to convert the low torque high-speed energy into high torque low-speed energy. As such, it is essential to keep all of the parts of the transmission in good working order to avoid a catastrophic equipment failure. However, several problems currently exist with this type of transmission that make the maintenance and/or repair of these components labor intensive and very expensive. One of these problems involves the inboard thrust washer, which is disposed within the transmission and is used to restrain the axial motion of the high-speed carrier. Unfortunately, current transmission designs do not allow for the easy access and removal of the inboard thrust washer. In fact, current configurations require a complete disassembly of the wheel to remove the inboard thrust washer. This is undesirable because these vehicles are extremely large and heavy requiring considerable cost and labor to replace this component. This is also undesirable because of the down time or opportunity cost due to the loss of use of the vehicle while undergoing repairs and/or maintenance. Every minute that these vehicles are not operating results in lost earnings for the operators of these vehicles, and thus can result in the loss of thousands of dollars for every hour the vehicle is inactive.